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CONO-SUR 2009 Problem 4

    Andrea and Bruno play a game on a table with 1111 rows and 99 columns. First Andrea divides the table in 3333 zones. Each zone is formed by 33 contiguous cells aligned vertically or horizontally, as shown in the figure.

    
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    Then, Bruno writes one of the numbers 0,1,2,3,4,50, 1, 2, 3, 4, 5 in each cell in such a way that the sum of the numbers in each zone is equal to 55 . Bruno wins if the sum of the numbers written in each of the 99 columns of the table is a prime number. Otherwise, Andrea wins. Show that Bruno always has a winning strategy.

    Dataset text AI-MO AoPS. Quoted with source.

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